1 mole of an ideal gas is at 4 atm pressure, occupies 5 L and has an internal en
ID: 2069209 • Letter: 1
Question
1 mole of an ideal gas is at 4 atm pressure,occupies 5 L and has an internal energy of
633.5 J. The gas is first cooled at constant
volume until its pressure is 1 atm. It is then
allowed to expand at constant pressure until
its volume is 7 L with an internal energy of
1465.5 J.
Find the heat added during this process.
Answer in units of J
Explanation / Answer
Change in internal energy equals heat added to the gas minus the work done by it. Delta U = Q - W => Q = Delta U + W Change in internal energy is: Delta U = U_final - U_initial = 1465.5 J - 633.5 J = 832 J Work done by the gas is given the integral W = Delta P dV from V_initial to V_final In the first part of the process the volume is constant, so no work is done. The second part is a constant pressure process. For such a process the work integral simplifies to: W = P * dV = P* (V_final - V_initial) For this process: W = 3*101325Pa *(7
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